Sorry to ruin your day but the national immunization survey is exempt from the national do not call list do to the fact it is a federal government agency the CDC can call you anytime it is a federal agency sorry for the bad news.
Doesn't seem like the CDC would have any reason to know if i had a landline telephone or not, and as a gov't agency you'd think that it would be easier for them to find out in some way other than calling everyone. I have no doubts that this is a scam.